Very low frequency, low cost, wide bandwidth and portability are all desirable assets for underwater acoustic projectors. Present flextensional designs such as the folded shell projector (FSP) taught in U.S. Pat. No. 5,805,529 by Purcell and the barrel stave projector (BSP) as described in U.S. Pat. No. 4,922,470 by McMahon et al are portable but operate at frequencies far above what is required. The DRDC-Atlantic moving coil projector (MCP) operates over the frequency band required but weighs many tons and is not easily deployable. That projector can produce sound levels in excess of 180 dB at 10 Hz.
Presently very low frequency sound sources are created either by using radiating pistons driven by large displacement-high force mechanisms, by airgun driven cavity collapse, by spark induced cavity collapse, by edge driven flexural disk projectors or multi-motor driven flexural disk projectors.
Present low frequency projectors such as the moving coil projector, airgun and sparker are typically heavy and expensive devices.